Pallets have long been used in transport and storage of goods. They are constructed from a variety of materials, but primarily from wood lumber. The lumber is often made from hardwood. A common wood pallet is made of two sizes of lumber. The thick size commonly has a cross-section of 31/2 inches.times.11/2 inches. Three pieces with this cross-section run in a first direction to form beams. Across these beams on the top and bottom are thinner pieces of wood nailed or otherwise fastened at right angles to the beams to form the top and bottom surfaces of the pallet. Thin pieces typically have a cross-section of 1/2 inch thick by 2 to 6 inches wide. It has been estimated that over 50% of the cost of pallets made of wood lumber consists of the cost of the lumber, assuming the pallet is shipped less than 200 miles from its construction site.
Other materials such as plastic and corrugated paper have also been proposed for making pallets. Recent U.S. Pat. No. 5,417,167, for example, discloses a pallet made from hollow plastic stringers and plastic deck boards. Another recent patent, U.S. Pat. No. 5,425,314, proposes a disposable pallet made of paperboard or like material. The cost of the materials is a significant disadvantage of pallets made from plastic and paperboard.
The construction of a pallet containing bamboo board has been suggested. The pallet is made of long wooden beams and multilayered bamboo fibre fabric, flame retardant and thermosetting adhesive (Abstract in World Patent Index of China Pat. No. 1079707).
Bamboo is widely grown in tropical areas of the world. It exists in a number of varieties. The structure of bamboo is strikingly different from that of trees and many other plants. The trunk of the bamboo plant is called the "culm." Nodes exist at various distances along the culm. The culm is hollow inside except where nodes exist. Some varieties of bamboo, such as Dendrocalamus Strictus, Guadua, Jimba, or Cana Bravo, produce particularly thick-walled culms. The culms of bamboo have a hard outer skin which provides a surface particularly resistive to physical damage.
The physical properties of bamboo are somewhat unique also. Bamboo is stronger than most wood which is used to make pallets. Bamboo is also more flexible and elastic. When flexed, it bends slightly and will not break as easily as wood. When flexed or deformed for a short period of time, it will return to its original configuration. Bend strength of a variety of bamboo has been reported in "Bending Strength of Guadua Bamboo," Int'l. Network for Bamboo and Rattan, Working Paper No. 3, 1994. As expected, the strength of bamboo is highly dependent on wall-thickness, for either round members or split specimens. Strength may also vary depending on position along the culm.
Bamboo is easily treated with chemicals, such as preservatives or fire retardants, if desired. Some methods, such as the Boucherie/Sap Displacement method, can be used which make it easier to treat bamboo than wood, because all the fibers in bamboo run in the same direction.
Once established, bamboo replenishes itself very fast. Therefore, bamboo culms can be cut every two to three years. Hardwoods may take twenty or more years to grow and when cut must be started again from small trees. Bamboo can be planted along permanent roads. Therefore, it can be transported easily to a factory. A very large volume of bamboo timber can be produced on small acreage, and bamboo responds economically to fertilizer and irrigation.
While a variety of materials have been suggested and utilized for constructing pallets, the inherent growth and strength properties of round and split bamboo culms have not been realized as components of pallets. Pallets and construction methods for such pallets comprising bamboo are needed.